#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
#include<math.h>
double fun(double x) {
	return x * exp(x);
}
int main() {
	double a ;
	scanf("%lf", &a);
	double l = 0, r = 30;
	while (r - l > 0.000001) {
		double mid = (l + r) / 2;
		if (fun(mid) > a) {
			r = mid;
		}
		else {
			l = mid;
		}
	}
	printf("%.4lf\n",l);
	return 0;
}